1. Field
This application relates to the field of body force measurement, specifically to those utilized in the medical and therapeutic setting and more specifically to those generated by the teeth lips and tongue.
2. Prior Art
Speech, language, and swallowing difficulties can result from a variety of causes including stroke, brain injury/deterioration, developmental delays/disorders, learning disabilities, cerebral palsy, cleft palate, voice pathology, mental retardation, hearing loss, or emotional problems and the difficulties can be either congenital, developmental, or acquired.
Speech-language pathologists assess, diagnose, treat, and help to prevent disorders related to speech, language, cognitive-communication, voice, swallowing, and fluency. Treatment modalities may include range of motion and isometric exercises of the oral mechanisms. These techniques facilitate coordination and strength of the speech and swallowing muscles. Labial (relating to the lips) and lingual (pertaining to the tongue) isometric exercises are completed with use of a tongue depressor. Strengthening is accomplished by repetitive isometric force against the tongue depressor. This is completed in the lateral directions (side to side), protrusion/extension (out), upward and downward directions. Labial isometric exercises can also include completion of a strong labial seal on the tongue depressor.
Diagnostic baseline data and therapeutic progress is measured by a subjective assessment of force against the tongue depressor by the Speech Pathologist. This measurement technique is very inaccurate as the perception of the exerted force is inexact and varies from session to session. Furthermore, from session to session patients may be treated by different Speech Pathologists with the outcome that their overall progress will be subjectively assessed by several clinicians.
Although several devices have been patented to aid in the assessment and treatment by speech-language pathologists all of these devices require the clinician to modify their clinical practice. One of the earliest tools was specified by Rumburg, in U.S. Pat. No. 4,585,012. In this device, a chin rest is utilized for patient registration (the physical connection between the patient and the fixed point against which measurements are taken). Once the patient is registered to the device, the patient pushes against a blade (presumably a tongue depressor) causing the blade to bend against a pivot point. Rather than directly measuring the applied force, it is indirectly measured by measuring the amount of bending of the blade with a dial caliper. Not only is this indirect measurement subject to variability due to variations in the blade, variations in anatomy from person to person will cause their tongue to contact at different points on the blade and therefore the system would not provide accurate measurements between patients.
The potential to obtain a reliable measure of tongue strength in multiple directions was first described by Durke et. al. in U.S. Pat. No. 4,697,601 back in 1987. The independent claim is for a device that uses strain gauges to measure tongue force simultaneously in three directions by having the individual push against a tongue cup. However, the device is essentially non-functional without its dependent claim of further including a bifurcated tooth plate fastened to the device, which serves as a means of patient registration. Otherwise, given the “rigid” nature of the measurement system, if the therapist were simply to try and hold the device in place while the patient pushes against it, the therapist influence could easily be as great, or greater, than the effect trying to be measured. In fact, without the bifurcated tooth plate, a subjective assessment by an experienced clinician is probably far more accurate than an unregistered “rigid” mechanical device held in a clinician's hand.
Patient registration is actually one of the primary differentiation points between devices designed to measure tongue strength and Masahiko Wakumoto et al, U.S. Pat. No. 6,511,441, even goes so far as to attach electrodes directly to the roof of patient's mouth. However, the most common method of patient registration is to use a mouth piece. For instance, both Staehlin et al, U.S. Pat. No. 5,954,973 and Robbins et. al., U.S. Pat. No. 6,702,765 employ a mouth piece that substantially conforms to the patient's anatomy as a means of patient registration. These customized mouth pieces are expensive to produce and expensive and time consuming for the therapist to employ in daily practice.
At the other end of the spectrum is the IOWA Oral Performance Instrument, Robin et. al. U.S. Pat. No. 5,119,831, which provides no fixed mean of patient registration. The clinician simply holds onto a tube placed into the patient's mouth, which has a pressure sensing bulb at its extreme end, that the patient compresses against another body part.
The IOWA Oral Performance Instrument is one of the few devices to be commercially available and it has been studied by numerous authors. In clinical practice it is most often used to measure the pressure an individual can exert against the roof (hard palate) of the patient's mouth. However, the company also sells what it calls a “lateral tongue bulb holder”, which is a rigid stick to which the measurement bulb can be adhered. Once adhered, the patient then bites down on the stick to create a registration point for side-to-side (lateral) and sticking out the tongue (protrusion) measurements. Therefore, for lateral and protrusion measurements the patient is required to not only push against the bulb but to simultaneously bite down to keep the device in place, just as would be required with Durke's device previously mentioned.
Therefore, in order to obtain an accurate measurement of tongue strength all of the present devices require the patient to be registered to the device. This very act of patient registration requires clinicians to change their current clinical practice. Thus there is a continuing need for body force measurement systems that provide accurate quantifiable data that does not require clinicians to modify their clinical practice.